Over thirty million American suffer from debilitating neurological disorders. The ability to treat many of these diseases and dysfunctions of the central nervous system is quite limited. The studies conducted on the present grant critically examine a promising new approach of using neural transplants to replace dead or damaged neural tissue. The first six years of research have focused on elucidating factors important in neural transplant survival and function. Studies over the next three years will continue this line of investigation. An additional series of experiments will be initiated to address issues relevant to the possible clinical application of neural transplants. The ultimate goal of the studies conducted on this grant is to provide a better understanding of the factors important in the response of the brain to injury and recovery of function. It is hoped that these experiments will suggest better methods of treating neural dysfunctions in man. The specific goals for the next three grant years are: 1. To quantify the effects of physical and chemical lesions on transplant survival and function. 2. To critically analyze the influences of steroid hormones on grafted peptidergic neurons. 3. To evaluate alternatives to using fetal tissue as donor tissue in neural transplantation. 4. To determine if graft behavor in rodents is a good predictor of graft behavior in nonhuman primates. The studies proposed require a multidisciplinary research team approach. The basic and clinical scientists participating in this research program have six years of experience in working together. The techniques necessary to accomplish the goals outlined are in use in our laboratories.